Embodiments of the present invention relate to the field of gas turbines. In particular, embodiments of the present invention relates to valves for use in the fuel supply systems of such turbines.
The fuel systems of the industrial gas turbines burn a mixture of fuels, such as oxygen and a gas or liquid fuel. These multi-fuel gas turbines generally do not simultaneously use liquid and gaseous fuels, but are alternately supplied with one fuel and then another. Changeover of the fuel supply is typically time-consuming and following such a change in fuel, the supply of that fuel is fixed until a subsequent changeover.
In such multi-fuel gas turbines, stagnant liquid fuel can undergo solidification at high temperatures and in the presence of air. This phenomenon is known as “coking”. This solidification may result in deterioration of sensitive elements of the turbine and of the sealing function of mechanical components, such as valves and check valves. It may also give rise to a reduction of fuel flow speeds in the turbine.
In order to resolve these disadvantages, it is known to remove residual liquid fuel in the supply system through a drain by admitting pressurized air. This drainage function is intended to clean the supply system, particularly in high temperature areas close to the turbine. However, this drainage function has limited efficiency. In fact, since the pressurized air used is compressible, variations in the flow of liquid fuel towards the turbine fuel chamber can occur during drainage. This can result in power trips. Moreover, this drainage can also cause accumulation of air in the supply system, which can also result in power trips. These power trips are problematic in that they can trigger overspeed or high temperature alarms at the exhaust of the turbine.
In an attempt to resolve these problems, residual liquid fuel has firstly been drained by passing pressurized water through the liquid fuel supply system and then, the water drained by introducing pressurized air. Such an approach is described in FR-A1-2 938 048
The fuel system includes check valves provided within the liquid fuel supply circuit and on the purge air inlet circuit which are positioned close to the fuel chambers of the turbine. The proximity of these valves to high temperature areas of the turbine may result in a deterioration of the spring tension associated with the valves in an open or closed position.
Embodiments of the present invention are aimed at resolving these problems.
More particularly, it is an object of embodiments of the present invention to provide devices that, on the one hand, avoids the presence of residual liquid fuel in the turbine supply system that may form a residue that tends to solidify in the presence of air and at high temperatures, and on the other hand, to increase the reliability of the turbine.